1. Field of the Invention
This invention relates to a coloring apparatus and process, such as a dyeing or printing process for a leather. More particularly, the present invention relates to a leather coloring process, and a leather coloring apparatus, that enables highly minute image formation on leather by a simple and high-speed operation.
In addition to the above, the present invention also relates to a coloring treatment process attaining a simplification for various finishing processes, and a coloring treatment apparatus thereof, as well as also relating to a leather produced after such leather coloring and a leather product obtained by processing the leather.
2. Related Background Art
Leathers are commonly produced according to the following processes. First, raw hide or skin obtained by skinning animals is subjected to a preliminary, beamhouse process comprised of soaking, fleshing, unhairing, liming, splitting, scudding, washing, re-liming, deliming and bating subsequently to a tanning process to carry out tanning by the use of a tanning agent of various types such as chromium compounds and vegetable tannin in order to impart softness and thermal resistance to the hide or skin, and thereafter a dyeing and fatliquoring process comprised of neutralizing, dyeing and fatliquoring (or stuffing), finally followed by a finishing process comprised of sammying, setting-out, drying, conditioning, staking, stretch drying, trimming, grain correcting, coating, and measuring, where durability, fastness and the like are improved. Having been subjected to these processes, leather products are obtained as final products.
Leather products are utilized in a great variety of fields, making the most of the handle (or hand) inherent in leathers. For example, they are utilized in a vast range of footware such as shoes, clothes, personal ornaments such as gloves and belts, traveling goods such as bags, trunks (or suitcases) and purses, industrial parts such as belts and gaskets, and furniture such as chairs and automobile seat sheets, as well as horse gear, musical instruments, kendo (Japanese style fencing) goods, and so forth. In such respective fields, hide or skin of various animals and various tanning methods are used. For such uses, hitherto in addition to dyeing the hide or skin in specified color in whole, at a finishing step, varieties in surface shapes as in embossing leather and suede are provided to make these types of leather products abundant and to exhibit a high-grade quality.
Under such circumstances, the coloring on leather by conventional dyeing or coating is carried out using dyes or pigments. Almost all of these coloring materials are those employed from dyes or pigments hitherto used in the dyeing of textiles, and coloring processes suitably selected according to the kind of raw hide or skin, the manner of tanning and the type of use. For example, there are processes such as battick dyeing, dip dyeing and textile printing.
Under actual circumstances, however, since the leather has various properties according to its kind, actual operation still largely depends on experience. Even when the leather is colored in monochrome, the coloring on some kinds of leathers takes a long time for its operation, requires complicated operation steps, or makes it necessary to repeat the same step many times. Hence, it has been very difficult to mass-produce dyed products of the same design or to dye leather to form highly minute images or multi-color images.
Meanwhile, the surface of leather, in particular, what is called the grain side of natural leather has irregularities or large concavities because of follicle mouths (pores of the skin) or various wrinkles originally present in raw hide or skin. If the leather is dyed in that state, dyeing agents may conspicuously gather to that part to cause highly deep-colored portions. Also when the leather is dyed after it has been smoothened to eliminate irregularities or large concavities in treating steps, it is difficult to perfectly smooth the surface, so that the leather may be non-uniformly colored or non-colored at the first operation. To overcome such disadvantages, it is often necessary to reform many steps or to repeat the operation of dyeing and rinsing several times. Namely, it is difficult to obtain the desired state of dyeing and the desired color tones. As a result, it tends to provide only leather products with varied color tones.
On the contrary, in the general trends of wanting to have products with a sense of high grade in everyday living goods and ornaments, leather products can also more highly enjoy the sense of high grade inherent in leather if products with highly minute images formed on the surface can be readily obtained, and also it is possible to intend an application of leather products in a wider range if it becomes possible to form multi-color images or to carry out partial printing on leathers with ease.
However, as previously stated, the hitherto known dyeing and coating processes require a large number of steps and hence take a long time for their operation, in order to maintain color density and fastness. Moreover, leathers are hitherto mostly dyed in monochrome, and hence, in order to represent multi-color images on leather, it has been necessary to stick or stitch sheet by sheet a plurality of leathers dyed in different colors. There has been also a limit in number even if some kinds of colors can be represented on the same leather. At any event, the manner of dyeing or coating may often differ for each color and also the dyeing or coating has been manually operated in many instances, so that the experience of the one performing the dyeing or coating process is a great factor which, shows in the final product. Thus, in the past, the dyeing on leathers has been mostly supported by know-how, and hence it has been difficult to automate the operation, resulting in a high cost.
Thus, it will be complicated in processes and high in cost to express minute image and multi-color image and further to make a partial image formation only by improving conventional dyeing methods.
The present invention was made taking account of the above problems in the prior art. An object thereof is to provide a process that makes it possible to color on leathers at a low cost and also through simple steps, and to produce highly minute images, multi-color images or partial dyeings and the like on leathers.
An ink-jet method is therefore proposed.
What is meant by xe2x80x9ccoloringxe2x80x9d (leather coloring) generally embraces terms such as dyeing, coating and coloring in monochromes and multi-colors as hitherto commonly used as technical terms. Hence, it includes all modes such as a mode wherein, after the leather coloring, coloring materials serving as color sources have permeated in the inside of leather, a mode wherein they have adhered to, or partly permeated in, only the surface layer of leather or in the vicinity thereof and a mode wherein they are superimposed in layers on the surface of leather.
An ink-jet system is used to provide an image formation with integration of dots by moving an ink-jet head integrally arranged with a plurality of orifices according to a desired image signal and by ejecting ink as droplets containing a coloring material from the orifices. Accordingly, it is very effective for attaining objects for obtaining high precise images, multi-color images and partial colorings, by making an orifice density in arranging high or ejecting inks of different colors from a plurality of ink-jet heads. It is enough of an invention to attain the object to apply the ink-jet system to the coloration of leather. However, it has become clear that some further specified technical subjects occur in a combination of a leather and an ink-jet coloration, in the course of study on attaining a high level image with the ink-jet system.
Namely, the first one of these specified technical subjects is that a water resistance in high level is required. Even a case of performing an ink-jet coloration to leather, high fastness for subsequent steps is necessary and further a conventional finishing step is also necessary. The finishing step is for an object to protect a leather surface, as well as to provide a beautiful appearance. Among them, in particular, impregnating and film forming materials using water as a solvent or a dispersing agent are often utilized as a pretreatment step for coating and base and inter coating steps. Consequently, after the formation of multi-color images by an ink-jet coloring, many chances to directly contact the images with water will occur, even if there is a fatliquoring step. A conventional dyeing operation includes dipping a whole leather in a dyeing bath containing a dye and water, to keep a larger amount of dye in the leather than a dyeing amount which the leather can contain, and then to wash out an undyed dye by means of a washing step, by which no hinderance has occurred in a finish coating step. On the contrary, in a case of carrying out an ink-jet coloring on leather, it is difficult to use a coloring material over a necessary amount and wash out an undyed dye because of bleeding between colors, a balance of color density and the like. Although a dyeing acceleration agent has been conventionally used, it is not effective in this case, because it is objected to mainly for keeping a dyeablity after washing. Therefore, in formation of high precise and multi-color images, a technical subject that a coloring material in a formed image will be dissolved into water in a finish coating solution will occur to deteriorate a image quality in case of utilizing a conventional finishing step, unless a water resistance in consideration of a point different hitherfrom is added.
The second one of these specified technical subjects is that it is necessary to suppress a change of color density depending on a deviation of penetration or expansion of a coloring ink when especially high level images are stably formed on a specified part of area or leather. An ink-jet coloring has an advantage to perform coloring on a part of leather more easily than a conventional method. However, it has been found that as each dot to be colored on leather is finer, a weight thereof to decide a quality of images is increased depending on a behavior of each dot on leather, i.e., a penetration of an ink in the direction of thickness or an expansion of an ink on a surface. Dyeing on a leather can be discussed based on dyeing sites capable of bonding with a coloring material similar to dyeing on a cloth, and it is said that the dyeing sites in a leather are much more different than that in a cloth. However, it has been also found that, in a case of leather made up by changing properties with a variety of treating steps, keeping a form of natural hide or skin taken from an animal, which is different from a processed textile such as a cloth, distribution conditions of the dyeing sites at surface and inside of leather are recognized to be uneven. It has further been found out that it becomes difficult to obtain uniform images with an ink-jet coloring, because a distribution conditions of the dyeing sites differ, when a portion of animal body differs. In a conventional method, countermeasures of increasing an amount of dye, elongation of a dyeing time or re-dyeing have been taken. However, it is not preferable in an ink-jet coloring to apply such similar procedures, because there is a high possibility of bleeding between colors or loosing of a balance of each color. Namely, it is a very important technical subject to make images stabler in either cases of mono-chrome or multi-color that penetration conditions or a deviation of expansion of each dot on leather is suppressed and that a deviation of color density depending on a difference of penetration conditions of a coloring ink or a disorder of dot form depending on a difference of expansion of droplets is prevented.
The third one of these specified technical subject is that, even if high level images can be obtained by an ink-jet coloring, it does not contribute to efficiency of a whole process to merely replace conventional steps. As described above, there are many steps from a raw hide to a leather product. Among them, a coating step is used for improving a sense of beauty or making a durability to a leather having been provided with a handle or a form after dyeing is finished, and a coating agent is commonly liquid. However, it is necessary to take much care for coating agents depending on a made up condition of leather, and then there may be a case to prepare a specified coating agent in advance. Although mechanization in steps of a blow coating, a curtain coating, a roll coating and so forth is considerably proceeded, there are many steps to require man power in moving leather, attaching a leather to a coating apparatus and so on, during a transfer from dyeing to coating steps, since a dyeing apparatus and a coating apparatus are separate. In particular, it is difficult to attach a leather automatically since a shape of leather is not regulated. Thus, it is very difficult to perform a continuous operation throughout a coloring step to a coating step utilizing a conventional procedure. As a result, a problem may occur in that it takes much time to perform these treatments. Consequently, it is important to solve problems of this working time in a mass production or a limited production of many kinds of products. Also a problem of waste material of dyeing and of heat source for drying arising from a dip dyeing procedure cannot be negligible. Accordingly, it is a technical subject that may become a hinderance in maintaining image quality and in cost to conduct an image forming on a leather by an ink-jet system. Thus, the present invention is to attain high precise images, multi-color images, dyeing in a part to a leather which are problems incapable to attain by a conventional method, as well as to solve a specified technical subject occurring therein at the same time.
Accordingly, the main object of the present invention is to carry out coloring on a leather rapidly and inexpensively, and in addition to the above, as a specified object, first to attain a water resistance, and second to attain formation of high precise images excellent in fastness by stabilizing penetration and bleeding conditions of a coloring solution, and third to enable continuous operation and automation for treatments after image formation to leather, and an apparatus to attain the object mentioned above as well as a leather product made thereby.
The objects mentioned above can be achieved by the present invention.
As a first embodiment, the present invention basically provides a leather coloring process for carrying out coloring on a natural leather or a natural leather having been subjected to degreasing, the process comprising the step of carrying out ink-jet coloring on at least a partial area of the natural leather.
As another mode of the first embodiment, the present invention also provides an ink-jet leather coloring apparatus comprising a means for changing the quantity of ink, when ink-jetted according to printing signals, in accordance with the type of a natural leather to be subjected to leather coloring; an ink-jet means; and a transport means for transporting the natural leather to a coloring zone of the ink-jet means in the state of non-contact with the ink-jet means.
As a still another mode of the first embodiment, the present invention provides a leather or leather product on which ink-jet leather coloring has been carried out by the process of the first embodiment as described above.
As a second embodiment, the present invention basically provides a leather coloring process having the step of coloring an image on a natural leather having been subjected to tanning, the process comprising;
a jet coloring step of jetting to the leather a liquid ink containing a coloring material, in the form of droplets corresponding with given information to carry out coloring; and
a permeation step of imparting to the leather a coloring material fixing agent capable of reacting with the coloring material of the liquid ink jetted in the form of droplets and permeable in the leather, to cause the latter to permeate into the former.
As another mode of the second embodiment, the present invention provides a leather or leather product on which ink-jet leather coloring has been carried out by the process of the second embodiment as described above.
As a third embodiment, the present invention basically provides a leather coloring process for forming an image on a leather by coloring, the process comprising;
a prior step of imparting to the surface of the leather an ink permeation controlling agent capable of reacting with a coloring material of an ink, at least at its area to which the image is to be formed by coloring;
a coloring step of coloring the image on the surface of the leather by an ink-jet means, at least at its area to which the ink permeation controlling agent has been imparted; and
a posterior step of imparting to the surface of the leather an image controlling agent capable of reacting with the coloring material of the ink in the leather, at least at its area to which the image has been colored by the ink-jet means.
As another mode of the third embodiment, the present invention also provides an apparatus for carrying out the leather coloring process described above, the apparatus comprising an ink-jet means for carrying out coloring on a leather to form an image on the leather, and a modifying means for imparting to the leather an image modifying agent capable of substantially modifying the image by the ink-jet means.
As a still another mode of the first embodiment, the present invention provides a leather or leather product on which ink-jet leather coloring has been carried out by the process described above.
Other preferred modes, features and embodiments of the present invention will become apparent from the following description.